1. Field of the Invention
The present invention relates to a mobile radio communications method, a mobile radio communications system, a base station controlling equipment and a mobile radio terminal device. Specifically, the present invention relates to a mobile radio communications method, a mobile radio communications system, a base station controlling equipment and a mobile radio terminal device, all of which make it possible to reduce power consumption of the mobile radio terminal device used in the mobile radio communications system capable of performing high speed and large capacity data transmission.
2. Description of the Related Art
In recent years, as advanced radio communications technologies have been disseminated, various kinds of mobile radio terminal devices are widely and generally used. Such mobile radio terminal devices include mobile phones, PHS (Personal Handy-phone System) phones, and Personal Digital Assistants (PDAs) or micro-computers each installed with a radio LAN interconnect device. With regard to mobile radio communications system for these mobile radio terminal devices, it is expected that service area will be more and more expanded, and types of service will be increasingly diversified, in the future.
Since such mobile radio terminal devices are small-sized and light-weighted, the mobile radio terminal devices can perform data communications taking their advantages of portability. In addition, unlike wire communications, the radio communications does not require cables to be laid. As long as the mobile radio terminal device is present in the same radio area as a communications network, the mobile radio terminal device can be connected with the communications network through an access point. Thus, the mobile radio terminal device connected to the communications network via the access point can quickly perform data communications with other data processing equipment provided on a Local Area Network (LAN), a Wide Area Network (WAN) and a Personal Area Network (PAN) in the communications network.
Recently in particular, various places, such as railroad station yards, airport lobbies and tea lounges in a town, are furnished with the radio LAN communications equipment which is termed as “a hot spot”. By use of this, as long as people have their mobile radio terminal devices with them, they can connect their mobile radio terminal devices to the Internet by use of the radio LAN communications equipment furnished at the hot spot and they can browse home pages, and can transmit and receive electronic mails.
In addition, if such mobile radio communications system is used in corporations, shops, offices and the like, they can reduce labor and expenses for the layout change of floors because a change of laying communication cables, such as LAN cables is no longer required. Moreover, an advantage is brought about, where persons who frequently move from one section to another, or from one building to another, can make communication simply and quickly without doing conventional work of connecting their mobile terminal devices directly to the fixed cable which have been laid and provided in their destinations.
However, in environments where such mobile radio communications system is used, the power supply facilities for mobile radio terminal devices are not provide nearby in many cases. For this reason, basically, mobile radio terminal devices are driven by use of their built-in batteries.
Furthermore, in the case of the conventional mobile radio communications system, a data transmission rate has not been so high, and accordingly the data communications of small capacity with low power has been a mega-trend. However, recent mobile radio communications system can perform data communications at high transmission rate, which is by no means inferior to the wire communications, and accordingly the recent mobile radio communications system has been able to provide radio communications environments in which high speed data transmission with large amounts of data, such as image data, is available. In response to this trend, high speed and large capacity of data communications, power consumption of mobile radio terminal device has become remarkably larger.
Moreover, data transmission errors would occur in the mobile radio communications system if the propagation condition of radio signals is not suitable due to the location of the mobile radio terminal device, particularly on environments where obstacles and noise source of radio signals exist nearby. For this reason, retransmission of data is sometimes required in such a case, and causes data throughput to be degraded. Otherwise, the data throughput is likely to be degraded due to another factor which is causing the data transmission rate to become lower. Even in the case where the data throughput is degraded in this manner, time needed for the data communications is not so largely affected as long as the amount of data to be transmitted is small. However, in a case where the amount of data to be transmitted is large, time needed for the data communications is largely affected by the data retransmission. Also, as it is difficult for the mobile radio terminal device to discriminate the transmission condition of data under current environment, the mobile radio terminal device of the transmitting side transmits a large amount of data to the mobile radio terminal device of the receiving side irrespectively of what condition the receiving side device is placed in. This may cause data: transmission errors, and a data block is likely to be missing. In a case where the missing data block is to be retransmitted once again, if the data block is large in size, it takes long time for the retransmission of the data block. Accordingly, it causes larger power consumption of the mobile terminal device.
In mobile radio communications technologies, there are various schemes, including Time Division Multiple Access (TDMA) and Code Division Multiple Access (CDMA). Descriptions will be provided for CDMA, as an example. This communication scheme includes a function of data transmission rate alteration for performing high-speed data communications. This function alters the data transmission rate depending on the transmission condition such as noise levels of the radio zone for the mobile radio communications. Accordingly, alteration of the data transmission rate is controlled with a priority given to performance of high-speed data communications.
In this respect, in a case where the remaining capacity of electricity in the battery of the mobile radio terminal device is enough, it does not matter that the data, transmission rate is controlled with a priority given to the performance of the data transmission speed. However, if the data transmission rate is controlled with a priority given to the performance of the data transmission speed similarly when the remaining capacity of electricity in the battery of the mobile radio terminal device is insufficient, electricity in the battery is consumed by the same large power consumption, and electricity in the battery will run out shortly. As a result, the data transmission by the mobile radio terminal device is no longer continued. Moreover, in almost all cases, the power supply facilities for use of battery recharge are not available nearby. This is a serious problem for use of the mobile radio terminal device, and this is not only a problem with development of batteries, but also a constant problem with mobile radio communications system. That is because, even if small-sized large-capacity batteries are developed, the data communications service by the mobile radio communications system will be expectedly performed at a yet higher speed.
With this taken into consideration, the technology for reducing power consumption of the mobile radio terminal device is one of the important targets to be developed. Especially, the technology, which is able to control the power consumption when the remaining capacity of electricity in the battery has become short while the mobile radio terminal device is performing high-speed and large-amount data transmission, is sought.
Japanese Patent Laid-open Official Gazettes mentioned below have disclosed some technologies for reducing power consumption of the mobile radio terminal device.
Japanese Patent Laid-open Official Gazette No. 2002-208887 has disclosed a technology for reducing power consumption of mobile phones which are present out of communication coverage. In the case where a mobile phone is present out of communication coverage, the mobile phone not only can make no communication, but also has no stand-by channel. For this reason, the mobile phone is put in a state of performing channel scan for the purpose of searching for a possible stand-by channel. This makes the mobile phone consume power, and hence electricity in the battery is consumed in a large degree. If the mobile phone is out of the communication coverage for a time longer than a predetermined time, this means that the mobile phone is in a state of being unable to make communication. For this reason, the mobile phone temporarily turns off the power supply, and thus prevents power consumption.
Japanese Patent Laid-open Official Gazette No. 2000-278165 has disclosed a technology for reducing power consumption of the mobile radio terminal device by means of switching a part of functions of the circuit arrangement of the mobile radio terminal device under predetermined conditions. According to this technology, which is a technology of reducing power consumption for the CDMA mobile phone device, different numbers of analog-digital (A/D) conversion bits are used in the analog-digital converter during a stand-by state and a call state respectively. During the stand-by state, the number of A/D conversion bits to be used is smaller than the number of A/D conversion bits to be used during the call state, therefore, power consumption of the A/D converter and the diffusion process calculating unit is decreased, and thus the power consumption of the CDMA mobile phone device during the stand-by state is reduced.
In addition, Japanese Patent Laid-open Official Gazette No. 2004-048550 has disclosed a technology for preventing unnecessary power consumption due to forgetting a function changeover in a mobile phone complex terminal which combines a plurality of functions in the mobile phone. According to this technology, it is determined whether the position, at which the mobile phone is present, is in, or out of, service areas of the mobile phone. In a case where the mobile phone is out of service areas, the signal receiving unit of the mobile phone function is set in an OFF state. Thereby, reduction of power consumption is realized.
As well, an object of Japanese Patent Laid-open Official Gazette No. 2004-172772 has been to acquire a technology for receiving packets in a real-time manner in a case where the mobile radio terminal device has put in an intermittent power consumption reducing mode. According to this technology, the following steps are adopted for the mobile radio terminal. While the mobile radio terminal is being set in the intermittent power consumption reducing mode, the mobile radio terminal periodically detects an annunciation signal for packet transmission from the radio base station with a synchronized period of annunciation signal, and determines whether or not packets have come in. In a case where packets have come in, the mobile radio terminal determines whether or not real-time communication needs to be performed. When the real-time communication for packet receiving is required, the mobile radio terminal is turned to a normal mode all along until reception of the packets is completed.
Furthermore, Japanese Patent Laid-open Official Gazette No. 2000-069107 has disclosed a technology for switching transmission speed on the basis of the remaining capacity of electricity in battery detected by the mobile radio terminal itself.
However, in the cases of the technologies disclosed by Japanese Patent Laid-open Official Gazettes Nos. 2002-208887 and 2004-048550, measures to reduce power consumption are taken merely when mobile radio terminal device is out of communication coverage or out of service areas, and measures to reduce power consumption are not taken when the mobile radio terminal device is in communication coverage of in service areas. In the case of the technology disclosed by Japanese Patent Laid-open Official Gazette No. 2000-278165, measures to reduce power consumption are taken by different processes in respective stand-by and call states. However, it is not taken into account whether the remaining capacity of electricity in the battery is enough or short, therefore, the processing depending on the remaining capacity of electricity in the battery is not performed. Additionally, the technology disclosed by Japanese Patent Laid-open Official Gazette No. 2004-172772 is the technology for receiving complete packets even if the mobile radio terminal device is being set in an intermittent power consumption reducing mode. Therefore, it does not disclose measures to reduce power consumption depending on the remaining capacity of electricity in the battery. Moreover, in the case of the technology disclosed by Japanese Patent Laid-open Official Gazette No. 2000-069107, the mobile radio terminal device switches transmission speed by-detecting the remaining capacity of electricity in the battery. For this reason, a host equipment which communicates with the mobile radio terminal device as a counterpart can not recognize the reason why the mobile radio terminal device have changed the transmission speed.
In the case of the conventional technologies as described above, reduction of power consumption has not been realized systematically throughout the entire mobile radio communications system in the case where the remaining capacity of electricity in the battery of the mobile radio terminal device has become short while the mobile radio terminal device is performing high speed and large capacity data transmission.